Polyphase transformer tap-changing mechanism



May 9, 1939. K, BQLTE 2,157,814

POLYPHASE TRANSFORMER TAP-CHANGING MECHANISM Filed Feb. 8, 1957Inventor: Karl Bc'jlt,

His Attorney.

Patented May 9, 1939 PATENT OFFICE POLYPHASE TRANSFORMER TAP-CHANG- INGMECHANISM Karl Biilte, Karishorst, Germany, assignor to General ElectricCompany, a corporation of New York Application February 8, 1937, SerialNo. 124,733 In Germany February 13, 1936 1 Claim.

My invention relates .to polyphase transformer tap-changing mechanisms.In a polyphase transformer which has windings provided with tapconnections and switches for varying the voltage ratio of thetransformer, it is desirable that the switches be operated substantiallysimultaneously in order to prevent unbalance of the phase voltages forany appreciable period of time.

The general object of the present invention is to provide an improvedpolyphase tap-changing switch mechanism so arranged that the operationof any individual switch will automatically result in a substantialincrease of the operating force applied to the remaining switches andinstantly cause their operation. Thus, the time delay between theoperation of the switches will be extremely brief and there will be noappreciable unbalance of the phase voltages.

The invention will be better understood from the following descriptiontaken in connection with the accompanying drawing in which Fig. 1 is asimplified view of a three-phase group of switches with their operatingmechanism arranged in accordance with the invention, and Fig. 2indicates the application of the tapchanging mechanism of Fig. 1 to athree-phase transformer.

The tap-changing mechanism is shown in the drawing as being enclosed ina switch casing I0 mounted on one side of the main casing of athree-phase transformer i. The three windings l2, l3 and I4, which maybe either the primary or secondary windings of the transformer, are 35provided with taps connected respectively to the fixed contacts of threetap switches IS, IS and H. The movable contacts of these three switchesl5, I6 and I! are operated respectively by individual shafts ll, l9 and20 which are in turn operated through bevel gears by a common operatingshaft 2|. The three switches I5, I and H include spring connections 22,23 and '24 interposed respectively between the commonshaft 2| and thethree movable contacts of the switches. A common spring connection isalso interposed in the common shaft 2| which of course may be operatedby hand or from any suitable source 0' power, such as a motor.

when it is desired to change the voltage ratio 0 of the transformer, thethree switches l5, l6 and ll are operated by applying a torque to theouter end of the common shaft 2|. This torque, however, is opposed bythe resistance of the switches so that increasing tensions of the springconnections 22, 23, 24 and 25 are produced. It is obvious, however, thatthe tension of any one of the 5 spring connections 22, 23 and 24 is muchsmaller than that of the common spring connection 25.

As the torque of the common shaft 2| increases, the torque of each ofthe shafts I8, l9 and 2|! will of course increase until finally theresistance of 0 one of the switches |5, i6 and I1 will be overcomesufficiently to operate its movable contact with a snap action. Suppose,for example, that the resistance of the switch I5 is the first to beovercome and that this switch i5 is the first one 15 to operate. Thetension of the spring connection 22 will instantly decrease and itsopposition to the torque of the common spring connection 25 will besuddenly reduced. This will result in a sudden and simultaneous increasein the ten- 20 sions of both of the spring connections 23 and 24 andconsequently in the torque applied to the switches l6 and I1 which arealready about to be operated. This increased torque applied to these twoswitches l6 and I! will therefore cause them to operate with extremelysmall time delay after the initial operation of the switch l5. In likemanner, it is obvious that the operation of either of the switches IE orI! will automatically and instantly produce an increase in the torqueapplied to the other two switches and consequently result in theiroperation with substantially no time delay or unbalance of the phasevoltages.

The invention has been explained by describing and illustrating a simplearrangement of polyphase tap switches with a switch operating mechanismarranged in accordance with the invention, but it will be obvious thatchanges may be made without departing from the spirit of the inventionand the scope of the appended claim.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

The combination with a plurality of snap action tap switches for apolyphase transformer, of a common operating means including a springconnection for operating the switches, each switch including anindividual spring connection between itself and said common springconnection.

KARL BL'I'E.

